The small direct-fired boiler, once widely used for domestic heating, has been largely replaced in the home by gas and electric heat. It still finds utility on the farm and in light industrial applications and, because of the recent trend toward energy conservation, may be seeing a resurgence in residential applications.
This type of device is, of course, of ancient origin and thus the prior art is replete with teachings purporting to improve upon the basic design thereof. Some of these inventions are very old. By way of illustration are U.S. Pat. Nos. 404,524; 949,298; 560,848; 1,693,254; 1,512,480; 1,716,508; 1,825,326; and 1,794,953.
None of the foregoing, however, can claim the dramatic improvements in design efficiency of the instant invention. To familiarize the reader with the basic design, terminology, and problems typically encountered in the operation of the boiler, a description of the device would be helpful, to wit: the boiler consists of a firebox, over which is located some sort of heat exchanger which absorbs heat from the fire and transfers it to the fluid inside the exchanger. The fluid is typically water. This heat transfer device has traditionally been known as a "pancake" due to its resemblance to that early morning culinary delight, i.e., it is round and flat. Indeed, the heat exchanger often comprised a plurality of such pancakes or discs stacked atop each other in separated opposed relationship. The fluid is pumped through the exchanger, picking up heat, then circulated to the building or device to be heated and then back to the boiler to be recycled.
A major drawback to known boilers of this general type is that they must be shut down every few days for cleaning. The pancakes accumulate considerable soot and ash over their outer surface and in so doing, decrease considerably the amount of heat that may be transferred to the fluid. In addition, this accumulation may plug up the draft holes located in the pancakes which allow the smoke and fumes from the firebox to pass through to the chimney. The combustion products, having no alternative route, are then forced to eminate out of the firebox proper and into the surrounding environment. This can be most distressing if the boiler is located indoors.
From the foregoing it will be appreciated that a boiler improvement is needed which would eliminate the possibility of plugging, reduce the frequency of cleaning and improve the heat transfer characteristics of the boiler. Such an improvement is the teaching of the instant invention.